This invention relates to a system and to a method for grinding a circular saw blade.
Circular saw blades are used to cut various materials. In the timber industry, for example, lumber is manufactured from logs by cutting same into discrete board sections using differing types of saws including those having circular saw blades. Maintaining the saw blade teeth is important since blades which are not properly maintained produce substantial amounts of waste by-product.
Circular saw blades are conventionally ground employing systems including various types of circular grinding wheels to grind the saw blade teeth. The critical parameter in grinding a saw blade is "precise replication". All of the saw teeth in a given saw blade must be precisely ground to a similar configuration within extremely narrow tolerances. All of the individual saw blades in a given cutting system employing a plurality of such saw blades must be replicated in order to produce a uniform product.
Conventional grinding apparatus typically employ hydraulic devices, such as hydraulic cylinders and the like, to move the grinding wheel from the retracted position into position for grinding, and then move the wheel back to a retracted position away from the blade after the grinding operation has been completed on that particular tooth. The blade is then rotated to present the next tooth for grinding and the foregoing procedure is repeated.
Hydraulic cylinders, which contain a hydraulic fluid, have a fixed stroke length and vary speed by adjusting the hydraulic fluid pressure. However, hydraulic cylinders have a number of drawbacks. First, hydraulic cylinders inherently exhibit a limited degree of precision due to a limited sensitivity of response between the mechanical cylinder elements and the pressurized hydraulic fluid. Furthermore, hydraulic systems are sensitive to external surrounding conditions in the work area such as temperature and the like. For instance, the speed of movement of the wheel in the grinding cycle and the positioning of the wheel during grinding, respectively, will be affected by the temperature of the hydraulic fluid. Thus, if the hydraulic fluid is too cold, the viscosity of the fluid will be increased, the actuation speed and responsiveness of hydraulic cylinder will be slowed. The fixed stroke length of the cylinder may not reach a fully extended position and grinding replication will not be effected. This temperature problem is particularly difficult to control in an open, expansive manufacturing environment, particularly in a facility such as a timber mill. In addition to the above operational problems, hydraulic devices are relatively expensive to purchase and maintain.
A grinding system has also been employed in which an electrical motor is the driving means for moving the grinding wheel from a retracted position to a grinding position, and then back to a retracted position. The movement of the wheel between respective retracted and grinding positions is driven by a constant speed DC motor connected to a reciprocating mechanical crank system. The speed of movement is fixed by the rate of movement that is needed during grinding of each tooth. This yields very slow operation over the entire grinding cycle.
Therefore, there is a need for a more efficient grinding system which exhibits a high degree of precise replication not achievable using conventional hydraulic devices.